Vulnerability in pyssn1 (CVE-2026-59884)
Summary
Vulnerability in pyssn1 (CVE-2026-59884). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 0.6.4 or later.
Original description
The description as published by the source.
pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.4, the BER decoder shared by the CER and DER codecs parses long-form tags by accumulating continuation octets without an upper bound on the tag ID size, allowing a crafted input to force construction of an arbitrarily large integer with CPU cost growing quadratically and to trigger unhandled ValueError exceptions in Python 3.11+ error formatting paths. Any application decoding untrusted BER, CER, or DER input is affected. This issue is fixed in version 0.6.4.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-59884 has been found in pyssn1.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade pyssn1 to 0.6.4 or later.
If unsure, ask your IT team or search "pyssn1 CVE-2026-59884" on the vendor's site.
CVE-2026-59884 (pyssn1) — CWE-400 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 0.6.4 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-400) exists in pyssn1.
Check the vendor advisory for the affected versions of pyssn1.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 0.6.4.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'pyssn1' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'pyssn1' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
pyssn1を grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade pyssn1 to 0.6.4ステージング環境で 0.6.4 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- BellSoft Alpaquita BELL-CVE-2026-59884 py3-asn1 Fixed in: 0.4.8-r6
- Debian DEBIAN-CVE-2026-59884 pyasn1 Fixed in: 0.4.8-3+deb12u3
- Ubuntu UBUNTU-CVE-2026-59884 pyasn1
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- patch github.com
- web github.com
- web github.com
- web github.com